With development of a television and a display into resolutions of super-high definition (4K) and extra super-high definition (8K) and development and popularization of a new-generation cloud computing and information processing mode and platform adopting a remote desktop as a typical representation form, a video data compression requirement is also made for a higher-resolution composite image (or picture) including an image shot by a camera and a computer screen image. It becomes an indispensable technology of video coding for achieving an ultrahigh-compression ratio and extremely high-quality data compression.
Performing ultrahigh-efficiency compression on a video image by fully utilizing characteristics of a 4K/8K image and a computer screen image is also a main objective of a latest international video compression standard High Efficiency Video Coding (HEVC) as well as other international standards, national standards and industrial standards.
An outstanding characteristic of a computer screen image is that there may usually be many similar and even completely the same pixel patterns in the same image. For example, a Chinese or foreign character frequently appearing in a computer screen image is formed by a few basic strokes, and many similar or same strokes may be found in the same frame of image. A common menu, icon and the like in a computer screen image also have many similar or same patterns. Therefore, various copying manners are usually adopted in an existing image and video compression technology, at least including the following copying manners:
1) intra block copying, i.e. intra block matching or called as intra motion compensation or called as block matching or called as block copying;
2) intra micro-block copying, i.e. intra micro-block matching or called as micro-block matching or called as micro-block copying;
3) intra line (called as line for short) copying, i.e. intra line matching or called as line matching or called as line copying;
4) intra string copying, i.e. intra string matching or called as string matching or called as string copying or called as pixel string copying;
5) palette index string copying, i.e. palette or called as index string copying;
6) a mixed copying manner by mixing index string copying and pixel string copying, called as an index-pixel string mixed copying manner for short, also called as a palette-pixel string mixed copying manner or a palette manner mixing pixel string copying or a pixel string copying manner mixing palette or a palette and pixel string copying manner; and
7) a multiple palette and pixel string copying manner combining multiple palette and pixel string copying manners.
In a multi-pixel segment copying manner, for example, a micro-block copying manner, a line copying manner, a pixel string copying manner and a palette and pixel string copying manner, a coding/decoding block is partitioned into multiple pixel segments, each pixel segment has a copying parameter, and the copying parameter is formed by multiple types of copying parameters. In the multi-pixel segment copying manner, entropy coding or entropy decoding is sequentially performed on the copying parameters by taking a copying parameter as a unit according to a positional order of the corresponding pixel segments in the coding/decoding block. Since a copying parameter has both a binary code (called as bit or bin for short) part with entropy coding based on a Context Model (CM) and a bin part without entropy coding based on the CM, sequentially performing entropy coding on multiple copying parameters by taking a copying parameter as a unit may cause interleaved entropy coding on bin parts with the CM and bin parts without the CM of the copying parameters. Such an interleaving method seriously influences multi-bit parallel entropy coding and entropy decoding processing of the copying parameters and reduces an entropy coding and entropy decoding throughput.